The present invention relates to a refrigerating device. More specifically, the present invention relates to a refrigerating device using R32 (chemical formula CH2F2) or a mixed refrigerant containing at least 70% by weight of R32 as a refrigerant alternative to R22 (chemical formula CHClF2)
Challenges for protection of global environment relating to a refrigerating device and an air conditioner using a refrigerant to perform a refrigerating cycle include (1) protection of the ozone layer, (2) energy saving, (3) response to global warming (restricted emission of CO2 or the like) and (4) recycling of resources. Particularly in view of protection of the ozone layer among these challenges for protection of global environment, R22 (HFC22) is not considered to be a favorable refrigerant due to its high ODP (Ozone Depletion Potential). Candidates of a refrigerant alternative to R22, which has a high ozone depletion potential, include R410A (having a composition of HFC32:HFC125=50:50 in weight ratio), R407C (having a composition of HFC32:HFC125:HFC134a=23:25:52 in weight ratio), R32 (HFC32) and so forth. Furthermore, some of refrigerating devices using R410A or R407C to perform a refrigerating cycle which can obtain a COP (Coefficient of Performance) equivalent to that of R22 are already commercially available.
However, when R410A or R407C is used, the size of a heat exchanger serving as a condenser needs to be increased in view of energy saving in comparison with the case where R22 is used. In particular, when R410A is used, this tendency becomes strong since the degree of supercooling (subcool (deg.)) in the condenser needs to be increased. Therefore, conventionally, the ratio m (=Vout/Vin) of the internal volume Vout of a heat exchanger serving as a condenser and the internal volume Vin of a heat exchanger serving as an evaporator is set to be higher than 1.5. As a result, there are disadvantages in costs and product size. In particular, as in the case of an air conditioner, when a heat pump cycle is also performed by circulating the refrigerant in a direction opposite to the refrigerating cycle, the refrigerant circuit needs to include a large-size liquid receiver (receiver) and a large-size vapor-liquid separator (accumulator) because optimal amounts of the refrigerant filled in the refrigerant circuit at the time of cooling and heating are largely different. Therefore, there are further disadvantages in costs and product size.
Accordingly, it is suggested to use R32 (HFC32) instead of R410A or R407C. R32 has a Global Warming Potential GWP which is about ⅓ of that of R22, R410A or R407C, and therefore R32 is extremely effective for preventing global warming. However, the COP of R32 cannot become higher than that of R22 while the COP of R407C or R410A is substantially equivalent to that of R22. In other words, a refrigerating device using R32 in a refrigerating cycle has not practically obtained a COP which greatly exceeds that of R22 although a high COP can be theoretically expected from characteristics of R32. Furthermore, R32 exhibits the phenomena that pressure and discharge temperature are higher as compared with the case of using R22. In addition, there is a problem that safety consensus is hardly reached since R32 has microcombustion property. Therefore, R32 has not been used in an actual product as an alternative refrigerant in industries.
Accordingly, an object of the present invention is to provide an energy saving type refrigerating device responding to global warming in which, by using R32 having a low global warming potential (GWP) as a refrigerant, a heat exchanger can be made smaller than a conventional device one while a coefficient of performance (COP) higher than that of a conventional device is obtained.
The present invention was accomplished based on a finding by the inventors of the present invention that a tendency that a COP of a refrigerating device varies depending on the refrigerant amount (the whole amount filled in the refrigerant circuit) largely differs depending on the kind of the refrigerant, particularly between R32 and the other refrigerants such as R410A and the like. Specifically, when R410A is used for example, as shown in FIG. 5A, there seems to be a tendency that the COP gradually rises as the refrigerant amount increases, and that the COP reaches to a saturated point in the shown range. On the other hand, when R32 is used, there is a tendency that the COP shows a peak in response to the change in the refrigerant amount, and that the COP rapidly lowers as soon as the refrigerant amount is out of the range where the peak is obtained. The reason why a higher COP could not be conventionally obtained in the case of using R32 in comparison with the case of using R410A is that R32 was used in a range where the refrigerant amount was relatively large (1200-1300 g in the example of FIG. 5A). Here, attention should be paid to the fact that the peak value of the COP when R32 is used and the refrigerant amount is changed is much higher than the COP when R410A is used in an optimal refrigerant amount (1300 g in the example of FIG. 5A). Therefore, there is a possibility that the size of a heat exchanger serving as a condenser can be reduced by using R32 in a range of a COP equivalent to or higher than a conventional COP in the case of using R22.
The present invention provides a refrigerating device circulating R32 in a refrigerant circuit as a refrigerant to perform a refrigerating cycle, the refrigerating device comprising: a compressor in the refrigerant circuit; a first heat exchanger serving as a condenser; an expansion means; and a second heat exchanger serving as an evaporator, wherein a ratio m of an internal volume (Vout) of the first heat exchanger to an internal volume (Vin) of the second heat exchanger is set to be in a range of 0.7xe2x89xa6mxe2x89xa61.5.
In the refrigerating device of the present invention, R32 is used as a refrigerant, and the ratio m (=Vout/Vin) of the internal volume (Vout) of the first heat exchanger serving as a condenser to the internal volume (Vin) of the second heat exchanger serving as an evaporator is set to be in the range of 0.7xe2x89xa6mxe2x89xa61.5. Consequently, the internal volume of the first heat exchanger serving as a condenser, and therefore, the size of the first heat exchanger are reduced in comparison with a conventional case, particularly, where R410A is used. Therefore, this device has advantages in costs and product size. Furthermore, as described later, a COP which is equivalent to or higher than a conventional COP level when R22 is used can be obtained. Furthermore, even when a refrigerant is circulated in a direction opposite to a refrigerating cycle to perform a heat pump cycle as in the case of an air conditioner, the optimal amount values of the refrigerant filled in the refrigerant circuit at the time of cooling and heating are closer when R32 is used in comparison with a conventional case (R22 or R410A is used) as described later. Therefore, the refrigerant circuit does not need to include a large-size liquid receiver and a large-size vapor-liquid separator (accumulator), and hence this apparatus has advantages in costs and product size.
In one embodiment of the present invention, as the refrigerant, a mixed refrigerant containing at least 70% by weight of R32 is used.
The principle of the present invention is applied not only to the single R32 refrigerant, but also to the mixed refrigerant containing at least 70% by weight of R32, and the same operational effects as the above can be obtained.